Phase-controlled model-based overlay measurement systems and methods

Abstract

Overlay measurement systems and methods are disclosed that control the relative phase between the scattered and specular components of light to amplify weak optical signals before detection. The systems and methods utilize model-based regressional image processing to determine overlay errors accurately even in the presence of inter-pattern interference.

Description

[0001] claim of priority [0002] This application claims priority to US Patent Application Serial No. 61 / 863,469, filed August 8, 2013, which application is incorporated herein by reference. technical field [0003] The present invention relates to an optical overlap measurement system, and in particular to the use of phase control optics for imaging even when the overlapping target is substantially smaller than the target currently in use and surrounded by other patterns and Systems and methods for model-based regression methods for image processing to accurately measure overlay error. [0004] All documents cited herein are hereby incorporated by reference. Background technique [0005] Most finely structured devices (such as integrated circuit chips, microelectromechanical devices, etc.) are made of multiple layers of precisely aligned electrical or mechanical patterns. This pattern is typically formed via multiple high-precision photolithographic steps during fabricat...

AI Technical Summary

Problems solved by technology

However, it has a number of key disadvantages, such as the need for large targets, poor handling of weak overlapping signals, shallow depth of focus, patterns from around the target, and severe effects from imaging system aberrations, etc.

Therefore, existing image-based overlay measurement systems are not suitable for future applications, most of which require small targets, good handling of weak signals, good filtering of harmful interference or influence, etc.

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